Coalburning apparatus



Nov. .8, 1932. A. USDAHL' 1,886,577

COAL BURNING APPARATUS I Original Filed Feb. 10, 1925 3 Sheets-Sheet 1INVENTOR Adolph Ousdahl Nov. 8, 1 932. A SDAHL 1,886,577

GOAL BURNING APPARATUS Original Filed Feb. 10, 1925 s Shets-Sheet 2 l mI r 0/ I INVENTOR I Adolph Ousdahl Nov. 8, 1932. QUSDAHL 1,886,577

COAL BURNING APPARATUS Original Filed Feb. 10, 1925 3 Sheets-Sheet 5 502 1o 79 o 0 IO INVENTOR Adolpg Ouadahl z v 5- 6 mzr A ORNEYs PatentedNov. 8, 1932 UNITED STATES PATENT OFFICE? ADOLPH OUSDAHL, OF SEATTLE,WASHINGTON, ASSIGNOR TO AUTOMATIC CO AL BURNER 00., A CORPORATION OFWASHINGTON COAL BURNING APPARATUS Application filed February 10, 1925,Serial No. 8,295. Renewed December 1, 1980.

My invention relates to apparatus intended for use in furnaces forheating homes, apartment houses and the like. This application a,

is particularly directed to the burner or furnace end of the apparatus,including the means for delivering fresh coal to the fire, the deliveryof air to the fire,the handling of the fuel mass while burning, and theremoval of ashes. A companion application Serial No. 8,294, filedcoincidentally herewith relates more particularly to a control and drivemechanism for apparatus of the type here concerned.

The primary object of this invention is the provision of apparatus ofthe character described which will accommodate a'large or a small amountof fuel, as may be determined by the character of fire desired, andwhich will insure proper combustion of the fuel whatever the characterof the fire. Thus, when a hot, forced fire is desired, my device willproperly handle a sufficient quantityof I fuel, and will supply air inamounts and in a manner to insure proper and complete combustion of thefuel, and when a slow,- holding 7 them at a rate materially lower thanthe normal, that the fire will die down and perhaps be extinguished.These defects appear to be due chiefly to improper supply of air andimproper admixture thereof with the fuel. It is, therefore, an object ofutmost importance to provide a stoker of this type in which the supplyof air for combustion will be in such amounts, and its application tothe fire will be at such points and in such manner, as to insure, atwidely varying rates of feed of the fuel, proper combustion of the fueland proper regulation of the fire.

A further object lies in the provision of means for en'iploying the coalitself or the mass of burning fuel to maintain clean and free the grateapertures.

A further object is the provision of automatic means for collecting andremoving the ashes.

A further object is the provision of means whereby accumulations ofdust, a'shes, bits of coal and the like may be readily removed andcombinations thereof which are shown in the accompanying drawings,described in the specification and particularly defined by the claimsterminating the same.

In the accompanyin drawings I have shown myinvention in orms which arenow preferred by me, the modifications being chiefly to adapt the deviceto different types of fuel.

Figure 1 is aside elevation with parts broken away, and Figure 2 is anend elevation showing the general arrangement of the apparatus.-

Figure 3 is a vertical section along the axis of the feed screw, takenthrough the burner and associated parts.

Figure 4' is a section through one side of the apparatus, on the line4.f1 of Figure 3.

Figure 5 is a similar section taken at the opposite side of theapparatus, and showing a slight modification.

Figure'G is a sect-ion, substantially on the line 6-6 of Fi re 3.

Figure 7 is a detail elevation, with parts shown in section, of the ashsweeper ori scraper.

Figure 8 is a detail section on line 8 -8 of Figure .5. v

Figure 9 is a perspective view of a detail.

It will be understood that my present invention may be employed with anytype of fuel feeding mechanism, and the form shown' in Figures 1 and 2,which is at present preferred by me, and whlch forms the sub ecttohereinabove, may be replaced by any suitable mechanism. In thispreferred form' the coal drops from hopper 9 into a coal conduit 4 80within which a feed screw 8 advances it to the fire-pot, containedwithin a casing 2, and air is supplied to the pot from a fan 90, thelatter being connected to the pot through i a conduit 81. This latterair conduit is shown as surrounding the coal conduit 80.

The feed screw 8 and the fan 90 are shown as driven from a motor 91,operating through suitable gearing contained in a gear box indicated at92, to drive a sprocket wheel 93, and thus in turn to drive a shaft 94through a chain 98. The shaft 94 is connected to the feed screw 8through some such intermittent drive means as the clutch mechanismillustrated diagrammatically at 95, the control means for thisintermittent action being illustrated more or less diagrammatically at96. A chain 97 is shown as connecting the shaft 94 with a shaft 71 towhich is secured a screw 7 the latter being intended to remove ashesfrom beneath the burner and todeliver them to a suitable point, as, forexample, to an elevating arrangement 72 by means of which the ashes maybe delivered to a can '73 or othersuitable receptacle. Inasmuch as theseconstructions form part of and are more fully described in my companionapplication, further description here is deemed unnecessary.

The present invention is concerned with the means for handling andburning the fuel after it has been delivered by the feed screw 8 intothe fire pot, and the means for removing ashes from the burner itself.The burner, as has been stated, is enclosed within a casing 2, whichcasing is .formed with an open top and preferably with one end, thatopposite the end at which the feed screw en- 'ters, being also open.Within this casing is formed a cup 3, the cup being fixed within thecasing and spaced from its walls and the fuel conduit 80 connecting toone side thereof (Fig. 3), the feed screw 8 extending thereinto todeliver coal to the bottom of the cup and to advance it upwardtherethrough by pressure of coal from beneath. Above the cup ispositioned the annular burner or grate l the walls of which aresubstantially vertical,'but fiaredoutwardly at the top, this burnercovering the open top of the casing 2 and extending over the upper edgethereof, but leaving free a central aperture for the discharge of coal.In effect this burner. forms a continuation of the cup 3, and these twoelements together form the burner pot. The space between the burner potand the walls of the casing 2 form an air chamber 20 through which theair for combustion of the coal, received from conduit 81, is fed to theburner. I

The burner or grate 1 is rotatable relative to the casing 2 and cup 3.It is shown as vice is rendered easy.

.ceived lugs 41 upstanding from the ring 4.

The bottom surface 13 of the burner is horizontal and is preferablyfinished to fit upon a similarly horizontal and finished upper surface31 of the cup 3. These two surfaces, fitting together, form a jointwhich will .prevent passage of any but the finest partlcles of coal andof any appreciable amount of air. To enable proper seating of these twosurfaces, leveling means may be employed between the ring 4 and grate 1,such as the leveling screws 14. Centering and clamping screws 19 may be.employed to retain the grate in proper position upon the ring 4, and thering may be retained in proper position by screws 49, which are onlyaccessible after removal of the grate.

' Rotation of the ring 4 and consequently of the annular gratel issecured in any suitable manner, and conveniently through the conveyor orfeed screw 8 at the burner end of the apparatus. For this purpose I haveshown a shaft 38 journaled in a side of the cup 3 and having operativeengagement with the endof the feed screw 8, as indicated at 39.Preferably this arrangement is in the form of axially interlockingfingers, as shown in Figure 3, whereby the feed screw may be withdrawnaxially from engagement with the shaft 38. Upon this shaft, in thechamber 20, is secured a bevel pinion 37 meshing with a bevel gear 43upon a vertical shaft 40. This vertical shaft is supported within thechamber 20 in some suitable manner, as in bearings 24 in-a cover plate23 which closes the open end of the casing 2. By thus supporting itassembly or disassembly of the de- At the upper end of the shaft 40 issecured a spur pinion 44, meshing with a ring gear 45 secured to thering 4. By such means the ring 4 and annular grate 1 are rotated as thefuel is fed into the fire,

ly to the chamber 20 to deliver air thereinto' from the fan 90. Air isthus supplied through the apertures 12 directly to the fire in theburner, and by locating these apertures towards the edge of the burnerit is insured that air will be supplied in such man ner as to insurecomplete combustion of the previously ignited coal. Ordinarily when theemployment of the helical ribs in consuch apertures are employed in aburner or grate they will in a short time become clogged with ashes,with bits of coal and with clinkers. By rotation of the burner 1 theburner is moved past the burning mass and a scouring'action ensues, bymeans of which these apertures 12 are maintained free. This isespecially true when means are provided for insuring to a large extentthat the mass in the burner will not rotate also, and is assisted bmeans which feed the material upward t ough the.burnerpot, and formoving it thus transversely of the apertures 12. This latter meanscomprises a rib 15 extending helically about the' interior of the burner1 and inclined with respect to the direction of rotation so that it willadvance the coal therein upward toward the curledover edge 10. Themeans, for insuring that the coal will not rotate with the burner, maybe any found suitable, but for this purpose I have found one 'or morepillars 5 or 5' positioned in the burner-pot but eccentrically of theaxis of rotation of the burner, to be suitable for the purpose. wo suchpillars are employed in the embodiment shown.

My burner is intended to burn either coking or non-coking coal, but theinherent characteristics of such coals require variation in the mannerof handling them, and in the manner of supplying air to the burningmass. In Figures 3 and I have shown a pillar 5 which is of a typeintended for use wlth coking coal, and in Figure 5 I have shown a pillar5' intended more particularly for noncoking coals. The chief differencelies in the fact that the pillar-5 is arranged in such a manner thatupon rotation it will breakup masses of coal in the burner-pot, whereasthe pillar 5' serves principally to supply additional air to the centerof the burning mass inside of the burner. In either type the primaryfunction is to revent, to a large extent, the rotation with the burnerof the burning mass therein. Both types of pillars are perforatedpreferabl for admission of air, the air being supplied to a chamber 50within the pillar through a hollow shaft 51, this extending verticallythrough a bore 35 in the cup 3;

If desired, and as'shown in Figures 3 and 4, the pillars may be somounted upon the upper end of the shaft 51 that upon rotation of theshaft the pillars will rotate, and to assist in breaking up the massesofcoal which tend to form when coking coal is burned, the pillars 5 areinclined relative to its axis and may be provided with a helical rib 55.By making the inclination of the pillars 5 substantially at the sameangle as the angle of the adjacent side wall of the burner 1, and byjunction with the rib- 15 on the inside of the grate, the action of therib 15 is augmented by the action of the ribs 55, the pillars thusserving the dual purpose of breaking up the mass and of raising theparticles, thus further preventing clogging of the holes, both in itselfand the apertures 12in the burner. Rotation of the shafts-51 is securedby any suitable means where rotation is desired. As shown herein asprocket 52 is secured to the lower end of each such shaft, and a chain45 passes about each of the sprockets 52 and about a drive sprocket 46upon the shaft 40, whereby upon rotation of the shaft 40 the shafts 51are rotated. This drive connection may be omitted if desired, and asshown in Figure 5, wherein the hollow shaft 5lserves merely as apositioning means and as a conduit for air from the chamber 20 throughthe apertures at the top of the pillar 5 and thus into the burner-pot.

It is inevitable that particles of ashes, soot, coal, and clinkers willfrom time to time pass through the apertures 12 or 54 and will drop intothe air chamber 20 within the casing 2. Means must be provided forremoving these particles and to this end I have shown the bottom of thecasing as having a series of apertures 26, these being normally closedby a shaker plate 6 which has apertures 62 adapted upon movement fromthe normal position of the plate 6 to register with the apertures 26 inthe bottom of the casing 2. The shaker plate is movable in the bottomas, for example, being pivotedat 61 in the center of the bottom and issuitably controlled preferably from a distant point. This may beaccomplished through a rod 60 secured to a link 63 secured to the shakerplate 6 at 65. By moving the rod 60' backwards and forwards the shakerplate is actuated. Stops, such as the shoulders 64 on the shaker plateand a pin 66 in the bottom of the casing, serve to indicate when theholes 62 and 26 are in and out of registry.

The coal as it burns forms ashes which by the addition offresh coal fromthe bottom of the burner-pot, are pushed outward over the edge 10 of theburner whence they pass in substantially equal quantities at a pluralityof 'points around the vertical center line of the burner, or, morespecifically, whence they pass substantially uniformly around thecircumference and vertical center line of the burner. I provide a ring79 having a peripheral flange 70 upstanding therefrom to receive theseashes. The ring is positioned below the edge 10 of the grate and allashes forced over this edge fall upon the ash-receiving ring 79.Inasmuch as the burner rotates, it is possible by providing one or moresweepers or scrapers as 17, pivoted at 18 upon the grate, to cause thisscraper 17 to move over the ring 79, that is to say, in an annular pathto which the ashes from the burner find their way and to sweep the ashesin front of it. Then by providing a localized opening or hole in thebottom of the ring 79 communicating with a spout 7 4 (Figures 1 and 2)the ashes may be swept around to the spout 74 and dropped therethroughinto position to be carried away by the screw 7 as has been previouslydescribed.

It is believed the operation of the device will be clear from the abovedescription. Fuel from the hopper 9 is fed through the conduit 80 by thescrew 8 directly into the bottom of the cup 3 forming part of theburner-pot. Itisraised primarilythroughthe action of the screw 8 intothe upper part of the burner-pot, where it finally becomes heated andignites. The rotation of the burner 1 serves to main? tain its airsupplying apertures 12 open, and

in effect maintains the fire fresh and bright through relative movementof the burner and fire such as occurs when the ordinary furnace grate isshaken. The effect is the same as would be secured by continuous gentleshaking of such a grate. It serves also to raise the burning massthrough the action of the helical rib 15. The pillars 5 or 5 supplyadditional air to the interior of the mass and prevent rotation of themass of coal. In addition, for coking coal the pillar 5 serves to breakup the mass and to raise it. The coal will become consumed in its upwardpassage through. the

annular burner l and the ashes will pass outward over the edge thereof,being forced out by the supplying of more coal from below and by thefeeding action of the rib 15. The ashes are received in the ring 79 andare scraped therefrom by the scraper 17 to be delivered to the chute 7 4and finally to be removed to the receptacle 73. i

One advantage of this type of burner is that when it is desired to burnmore coal, that is, to force the furnace, it is possible to do so merelyby increasing the speed of. the feed .screw and consequently'of theburner 1. Bo-

tation of the burner serves always to maintain its apertures clear andfree of obstructions, and to maintain the fire bright. Though thediameter of the burner may be small, this insures supplying suflicientair to the coal to fully consume it, between quite low and quite highfeeding, rates. Speeding up the feed screw in the arrangement shown,speeds up the fan 90 also and supplies additional air both through theapertures 12 and throughthe pillars 5 and 5'. The air is thoroughlymixed with the coal in such way that the coal is properly and thoroughlyconsumed. At the same time when it is desired to maintain a low firethis may be done by slowing down the rate of feed and the air supply.The feature of flexibility is one which is lacking in the. stokers ofwhich I am aware and is due chiefly to the rotary character of theburner and the manner in which the same maintains itself free ofobstructions, to permit the addition of the requisite amount of air tothe fire, and the manner in which ashes are constantly removed from theincandescent particles. The device-is also extremely simple to as sembleor disassemble and has no parts which need to wear or give out, exceptas the pillars 5 or 5' may burn out, and these are so arran ed that theymay be readily removed or repl aced.

What I claim as my invention is 1. In coal burning apparatus, a cup,means for feeding fuel upward therethrough, an annular burner forming anupward extension of said cup, means for rotating said burner relative tosaid cup, said burner having apertures thereabout for the admission ofair, and

having a helical rib extending about its inner wall to a point above thelower limit of said apertures.

2. In coal burning apparatus, a fixed cup, means for feeding fuel upwardtherethrough, an annular burner forming an upward extension of said cup,means for rotating said burner relative to said cup, and means fixedlylocated relative to said cup, and positioned within said burner andeccentric to its axis of rotation, and extending upward within the zonewhere coking begins, to intercept and break up masses tending to rotatewith said burner.

3. In coal burning apparatus, a two part burner pot, thelower portionthereof comprising a cup adapted to receive fuel, and the upper portioncomprising a rotative burner,

means for feeding fuel upward through said burner-pot, and'pillarssupported in and extending upward from said cup into the burner,eccentrically of the axis of rotation thereof, to intercept coalstending to rotate therewith.

' 4. In coal burning apparatus, a two part burner pot, the lower portionthereof comprising a cup adapted to receive fuel, the upper portioncomprisinga rotative burner, means for feeding fuel upward through saidburner pot, and means fixedl Qlocated relative to said cup and positionein said-burner pot eccentrically of the axis of rotation of the burnerto intercept coals tending to rotate therewith.

5. In coal burning apparatus, a two part burner pot, the lower portionthereof comprising a cup adapted to receive fuel, the upper portioncomprising a rotative burner, means for feeding fuel. upward throughsaid burner pot, and a helical rib upon the inner surface of said burnerinclined in a direction.

prising a cup adapted to receive fuel, and the upper portion comprisinga rotative burner forming an upward continuation of said cup, means forfeeding fuel upward substantially in astraight line through said burnerpot, an ash-receiving ring positioned beneath the outer edge of saidburner, and an ash scraper carried by said grate and movable therewithover said ring.

8.- Coal burning apparatus as in claim 7, said ash scraper comprising ashoe adapted to ride over said ring, and pivotally supported thereabovefrom the rotative member.

9. The combination with a burner of means for feeding fuel thereto andtherethrough,

a ring positioned about and beneath the edge of said burner, and anash-scraper carried by the burner and bearing upon said ring.

10. In coal burning apparatus, in combination, a casing open at its top,a ring rotative at the upper edge of said casing, means ac-' cessiblefrom within the ring to maintain it in place upon the casing, a rotativeburner mounted upon said ring to rotate therewith, means accessible fromwithout the burner for securing it upon said ring, means for feedingfuel upward through said burner,

and means for rotating said ring and burner.

11. In a coal-burning apparatus, a twopart burner pot, the lower portioncomprising a cup adapted to receive fuel, and the upper 'portloncomprising a rotative burner forming an upward continuation of said cup,means for feeding fuel upward through said burner pot, a pillar fixedlylocated relative to said cup and positioned within said burner eccentricto the axis of rotation of said ro ttative burner, means for rotatingsaid burner, and helical ribs on the interior of said burner positionedand co-operating with the pillar to lift fuel particles engaged therebyas it rotates.

In coal .burning apparatus, in combination, a casing interiorly dividedinto two coaxial chambers each open at its top, a burner membersupported upon the top of said casing, and extending. thereinto to closethe top of the outer chamber, the lower portion of the 1nner chambercomprising a fixed cup spaced from the outer wall of the outer chamber,and the burner member being fitted upon the upper edge of said cup andforming an upward extension thereof, said cup and burner memberconstituting a burner pot a ring rotative upon said casing and engagingwith said burner member for rotation thereof, means for feeding fuelupwards through said burnerpot, and means for ro tating said ring andburner member.

13. Acoal burning apparatus as in claim 12, the bottom of the casingbeing formed and adapted to be opened to release ashes fallingthereupon, and to be closed to confine air in the outer chamber.

14. In coal burning apparatus, in combination, a caslng open at its top,a ring rotative at the upper edge of said casing, a cup within saidcasing below its top, a burner member,

supported on said ring, and'havin a horizontal lower edge fittingclosely 't e upper means for leveling said burner member upon the ring.a

15; In coal burning apparatus, in combination, a casing open at its top,a non-rotative cup within said casing below its top and spaced from itsside walls, an annular apertured burner, member supported androtatableupon the upper edge of the casing, and fitting thereinto to close thetop of the easing, between its wall and said cup, the adjacent edges ofthe burner member and cup fitting closely together, a coal conduitextending into said casin and discharging into said cup, an air conduitconnected to said casing and discharging into the chamber thereindefined by the cup, the burner member, and the casing walls, means foradvancing fuel through said coal conduit into the on means for rotatingsaid burner member to eep the apertures in the latter free ofobstructlons, and apertured pillars supported in said cup and extendingupwardly through the burner member to prevent bodily rotation of thefuel mass therein contained the apertures in said pillars and in theburner member being in free communication with the air, chamber withinsaid casing.

16. A coal burning apparatus as in claim 15, including a rotative ringinterposed between said burner member and the upper edge;

of the casing, said ring resting upon and being rotative about thecasing burner member being secure to said ring.-

17. In' coal burning apparatus including an annular rotary burner memberand a stationary member therebelow, together constituting a burner pot,a. casing surroundmg said members and forming therewith a closed airchamber surrounding the burner pot, a

hollow upright shaft supported in the stationary member and extendingfrom said air edge, and said chamber to the rotary burner member, and anI apertured pillar having an interior, chamber in communication with thebore in said shaft, and supported on said hollow shaft to extend intosaid rotary burner member, to discharge air from said air chamberthereinto through its apertures.

18. In coal burning apparatus, in combination, a casing open at its topand at an end, a cup within said casing below its top and spaced fromits walls, an annular apertured burner member supported for rotationfrom the upper edge of said casing, and fitting within said casing, saidburner member forming an extension of said cup, and constitutingtherewith aclosure for the top of said casing, to define a chamberwithin said casing, a coal conduit discharging into said cup, a feedscrew rotatable in said conduit, a shaft extending through and journaledin a wall of said cup, said shaft and feed screw being opera'tivelyconnected, a cover plate for closing the open end of said casing, avertical shaft journaled on the inside of said cover plate,

and drive connections within said chamber between said two shafts andbetween the ver tical shaft and said burner member, to rotate thelatter.

19. Goal burning apparatus as in claim 18, characterized by theinterposition of a ring having gear teeth thereon between the burnermember and the upper edgeof the casing,

said ring resting upon the casing and supof, and means provided with alocalized opening to receive the ashes transported by the sweeperhereinafter mentioned, of a sweeper revolvable, around a vertical lineextending through said center opening in the burner, in an annular pathto which the ashes passing from the periphery of the burner find theirway, and means for revolving said sweeper in said path.

21. In a coal burning apparatus, the combination with a substantiallyannular burner,

means for feeding the coal thereto comprising means for forcing the coalupwardly through the center opening in the burner, the solidmaterial'thence passing outwardly and the ashes discharging from theburner substantially uniformly throughout substantially the entireperiphery thereof, and means provided with a localized opening toreceive the ashes transported by the sweeper hereinafter mentioned, of asweeper revolvable, around a ver tical line passing through said centeropening of the burner, in an annular path to which the ashes sodischarging from the burner find their way, and means for revolving saidsweeper in said path.

22. In coal burning apparatus, the combination of a substantiallvcircular burner, a stationary casing surrounding the vertical centerline of said burner and cooperating with said burner to form an airchamber from whence combustion air passes to the fuel on the burner,means for feeding coal to the center of the burner, whence the solidmaterial passes outwardly and the ashes are discharged from the burnersubstantially throughout the entire periphery thereof, a rotatable ringmounted on said stationary casing for rotation around said verticalcenter line, means for rotating said ring, and an ash sweeper carried bysaid ring for revolution in a path to which the ashes from the burnerfind their way, and means providedwith a localized opening to receivethe ashes transported by said sweeper.

23. The subject matter of claim 22, characterized by the fact that saidburner includes a rotatable part, and said rotatable part is mounted onand driven by the said rotatable ring.

24:. In a coal burning apparatus, a stationary upwardly open casingmember, a stationary upwardly open cup therein, spaced from asurrounding wall of said casing member to provide a space for thepassage of combustion air to the burner hereinafter mentioned, a burnerhaving a center opening to receive coal passing upwardly from said cupand extendingfrom above the edge of said cup across said space betweensaid cup and said wall of the casing member, means for forcibly feedingfuel both into a side of said cup and thence upwardly to said burner,the solid material thence passing outwardly and the ashes dischargingfrom the burner sub stantially throughout the entire periphery thereof,a ring rotatably mounted on said casing member for rotation around avertical line passing through said center opening of the burner, meansfor rotating said ring, and an ash sweeper mounted on said ring forrevolution thereby in a path to which ashes from the outer edge of saidburner find their way, and means provided with an opening for ashestransported by said sweeper.

25. In an automatic coal burning apparatus, the combination of acenter-underfed annul'ar burner, a solid-material conveyor below theburner serving the same, the solid material passing upwardly throughsaid burner and outwardly and the ashes discharging from the burnersubstantially throughout the entire periphery thereof, means for drivingsaid conveyor, a ring rotatable around a vertical line extending throughthe center opening of said burner, a connection, at the burner end ofthe apparatus, between said conveyor and-said ring for driving thelatter, and an ash sweeper carried by said ring for revolution in a pathto which said ashes from the burner find their way, and means providedwith a localized opening to receive ashes transported by said sweeper.

26. In coal burning apparatus, in combination, apparatus at which thecoal is burned oibly feeding coal upwardly through and over said grate,means for rotating said rotatable member, an ash sweeper, carried bysaid rotatable member, in the path of the ashes falling from said grate,and means provided with a localized opening to receive the ashestransported by said sweeper characterized by the fact that the burnedashes "are free to pass to the periphery of said grate,

under the thrust of fresh coal fed by said coal conveyor, substantiallyuniformly throughout substantially the whole of said periphery, and arefree to fall'th'erefrom, throughout substantially the whole of theperiphery of the grate as and when they are thrust to the grateperiphery by the thrust of the fresh coal.

Signed at Seattle, King County, Washington, this 4th day of February,1925.

ADOLPH OUSDAHL.

